#include <stdlib.h>
#include <clutter/clutter.h>

#define TARGET_SIZE     200
#define HANDLE_SIZE     128

static ClutterActor *stage   = NULL;
static ClutterActor *target1 = NULL;
static ClutterActor *target2 = NULL;
static ClutterActor *drag    = NULL;

static gboolean drop_successful = FALSE;

static void add_drag_object (ClutterActor *target);

static void
on_drag_end (ClutterDragAction   *action,
             ClutterActor        *actor,
             gfloat               event_x,
             gfloat               event_y,
             ClutterModifierType  modifiers)
{
    ClutterActor *handle = clutter_drag_action_get_drag_handle (action);

    g_print ("Drag ended at: %.0f, %.0f\n",
             event_x, event_y);

    clutter_actor_save_easing_state (actor);
    clutter_actor_set_easing_mode (actor, CLUTTER_LINEAR);
    clutter_actor_set_opacity (actor, 255);
    clutter_actor_restore_easing_state (actor);

    clutter_actor_save_easing_state (handle);

    if (!drop_successful)
    {
        ClutterActor *parent = clutter_actor_get_parent (actor);
        gfloat x_pos, y_pos;

        clutter_actor_save_easing_state (parent);
        clutter_actor_set_easing_mode (parent, CLUTTER_LINEAR);
        clutter_actor_set_opacity (parent, 255);
        clutter_actor_restore_easing_state (parent);

        clutter_actor_get_transformed_position (actor, &x_pos, &y_pos);

        clutter_actor_set_easing_mode (handle, CLUTTER_EASE_OUT_BOUNCE);
        clutter_actor_set_position (handle, x_pos, y_pos);
        clutter_actor_set_opacity (handle, 0);

    }
    else
    {
        clutter_actor_set_easing_mode (handle, CLUTTER_LINEAR);
        clutter_actor_set_opacity (handle, 0);
    }

    clutter_actor_restore_easing_state (handle);

    g_signal_connect (handle, "transitions-completed",
                      G_CALLBACK (clutter_actor_destroy),
                      NULL);
}

static void
on_drag_begin (ClutterDragAction   *action,
               ClutterActor        *actor,
               gfloat               event_x,
               gfloat               event_y,
               ClutterModifierType  modifiers)
{
    ClutterActor *handle;
    gfloat x_pos, y_pos;

    clutter_actor_get_position (actor, &x_pos, &y_pos);

    handle = clutter_actor_new ();
    clutter_actor_set_background_color (handle, CLUTTER_COLOR_DarkSkyBlue);
    clutter_actor_set_size (handle, 128, 128);
    clutter_actor_set_position (handle, event_x - x_pos, event_y - y_pos);
    clutter_actor_add_child (stage, handle);

    clutter_drag_action_set_drag_handle (action, handle);

    clutter_actor_save_easing_state (actor);
    clutter_actor_set_easing_mode (actor, CLUTTER_LINEAR);
    clutter_actor_set_opacity (actor, 128);
    clutter_actor_restore_easing_state (actor);

    drop_successful = FALSE;
}

static void
add_drag_object (ClutterActor *target)
{
    ClutterActor *parent;

    if (drag == NULL)
    {
        ClutterAction *action;

        drag = clutter_actor_new ();
        clutter_actor_set_background_color (drag, CLUTTER_COLOR_LightSkyBlue);
        clutter_actor_set_size (drag, HANDLE_SIZE, HANDLE_SIZE);
        clutter_actor_set_position (drag,
                                    (TARGET_SIZE - HANDLE_SIZE) / 2.0,
                                    (TARGET_SIZE - HANDLE_SIZE) / 2.0);
        clutter_actor_set_reactive (drag, TRUE);

        action = clutter_drag_action_new ();
        g_signal_connect (action, "drag-begin", G_CALLBACK (on_drag_begin), NULL);
        g_signal_connect (action, "drag-end", G_CALLBACK (on_drag_end), NULL);

        clutter_actor_add_action (drag, action);
    }

    parent = clutter_actor_get_parent (drag);
    if (parent == target)
    {
        clutter_actor_save_easing_state (target);
        clutter_actor_set_easing_mode (target, CLUTTER_LINEAR);
        clutter_actor_set_opacity (target, 255);
        clutter_actor_restore_easing_state (target);
        return;
    }

    g_object_ref (drag);
    if (parent != NULL && parent != stage)
    {
        clutter_actor_remove_child (parent, drag);

        clutter_actor_save_easing_state (parent);
        clutter_actor_set_easing_mode (parent, CLUTTER_LINEAR);
        clutter_actor_set_opacity (parent, 64);
        clutter_actor_restore_easing_state (parent);
    }

    clutter_actor_add_child (target, drag);

    clutter_actor_save_easing_state (target);
    clutter_actor_set_easing_mode (target, CLUTTER_LINEAR);
    clutter_actor_set_opacity (target, 255);
    clutter_actor_restore_easing_state (target);

    g_object_unref (drag);
}

static void
on_target_over (ClutterDropAction *action,
                ClutterActor      *actor,
                gpointer           _data)
{
    gboolean is_over = GPOINTER_TO_UINT (_data);
    guint8 final_opacity = is_over ? 128 : 64;
    ClutterActor *target;

    target = clutter_actor_meta_get_actor (CLUTTER_ACTOR_META (action));

    clutter_actor_save_easing_state (target);
    clutter_actor_set_easing_mode (target, CLUTTER_LINEAR);
    clutter_actor_set_opacity (target, final_opacity);
    clutter_actor_restore_easing_state (target);
}

static void
on_target_drop (ClutterDropAction *action,
                ClutterActor      *actor,
                gfloat             event_x,
                gfloat             event_y)
{
    gfloat actor_x, actor_y;

    actor_x = actor_y = 0.0f;

    clutter_actor_transform_stage_point (actor, event_x, event_y,
                                         &actor_x,
                                         &actor_y);

    g_print ("Dropped at %.0f, %.0f (screen: %.0f, %.0f)\n",
             actor_x, actor_y,
             event_x, event_y);

    drop_successful = TRUE;
    add_drag_object (actor);
}

int
main (int argc, char *argv[])
{
    ClutterActor *dummy;

    if (clutter_init (&argc, &argv) != CLUTTER_INIT_SUCCESS)
        return EXIT_FAILURE;

    stage = clutter_stage_new ();
    clutter_stage_set_title (CLUTTER_STAGE (stage), "Drop Action");
    g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);

    target1 = clutter_actor_new ();
    clutter_actor_set_background_color (target1, CLUTTER_COLOR_LightScarletRed);
    clutter_actor_set_size (target1, TARGET_SIZE, TARGET_SIZE);
    clutter_actor_set_opacity (target1, 64);
    clutter_actor_add_constraint (target1, clutter_align_constraint_new (stage, CLUTTER_ALIGN_Y_AXIS, 0.5));
    clutter_actor_set_x (target1, 10);
    clutter_actor_set_reactive (target1, TRUE);

    clutter_actor_add_action_with_name (target1, "drop", clutter_drop_action_new ());
    g_signal_connect (clutter_actor_get_action (target1, "drop"),
                      "over-in",
                      G_CALLBACK (on_target_over),
                      GUINT_TO_POINTER (TRUE));
    g_signal_connect (clutter_actor_get_action (target1, "drop"),
                      "over-out",
                      G_CALLBACK (on_target_over),
                      GUINT_TO_POINTER (FALSE));
    g_signal_connect (clutter_actor_get_action (target1, "drop"),
                      "drop",
                      G_CALLBACK (on_target_drop),
                      NULL);

    dummy = clutter_actor_new ();
    clutter_actor_set_background_color (dummy, CLUTTER_COLOR_DarkOrange);
    clutter_actor_set_size (dummy,
                            640 - (2 * 10) - (2 * (TARGET_SIZE + 10)),
                            TARGET_SIZE);
    clutter_actor_add_constraint (dummy, clutter_align_constraint_new (stage, CLUTTER_ALIGN_X_AXIS, 0.5));
    clutter_actor_add_constraint (dummy, clutter_align_constraint_new (stage, CLUTTER_ALIGN_Y_AXIS, 0.5));
    clutter_actor_set_reactive (dummy, TRUE);

    target2 = clutter_actor_new ();
    clutter_actor_set_background_color (target2, CLUTTER_COLOR_LightChameleon);
    clutter_actor_set_size (target2, TARGET_SIZE, TARGET_SIZE);
    clutter_actor_set_opacity (target2, 64);
    clutter_actor_add_constraint (target2, clutter_align_constraint_new (stage, CLUTTER_ALIGN_Y_AXIS, 0.5));
    clutter_actor_set_x (target2, 640 - TARGET_SIZE - 10);
    clutter_actor_set_reactive (target2, TRUE);

    clutter_actor_add_action_with_name (target2, "drop", clutter_drop_action_new ());
    g_signal_connect (clutter_actor_get_action (target2, "drop"),
                      "over-in",
                      G_CALLBACK (on_target_over),
                      GUINT_TO_POINTER (TRUE));
    g_signal_connect (clutter_actor_get_action (target2, "drop"),
                      "over-out",
                      G_CALLBACK (on_target_over),
                      GUINT_TO_POINTER (FALSE));
    g_signal_connect (clutter_actor_get_action (target2, "drop"),
                      "drop",
                      G_CALLBACK (on_target_drop),
                      NULL);

    clutter_actor_add_child (stage, target1);
    clutter_actor_add_child (stage, dummy);
    clutter_actor_add_child (stage, target2);

    add_drag_object (target1);

    clutter_actor_show (stage);

    clutter_main ();

    return EXIT_SUCCESS;
}